Filtration cassette and filtration system

Abstract

This technology enables more efficient filtration operation of treatment tanks. [Solution] The filtration cassette installed in the treatment tank comprises a housing having side walls and a bottom wall, and a filter material housed within the housing and forming a filtration layer. The side wall includes an inlet wall portion into which the water to be treated flows, and an outlet wall portion located on the opposite side of the inlet wall portion, with the filtration layer in between, through which the water to be treated flows out. A water-permeability prevention section is provided on at least one of the inlet wall portion and the outlet wall portion, which is the wall where the prevention section is installed, to prevent the passage of the water to be treated and the filter material. The water-permeability prevention section is installed in the area of ​​the prevention section installation wall from the position of the bottom wall in the vertical direction to at least the position of the lower end of the filtration layer, so as to prevent the passage of the water to be treated and the filter material.

Description

Technical Field

[0001] The present invention relates to a filtration cassette and a filtration system installed in a treatment tank.

Background Art

[0002] Conventionally, in a water treatment plant, a sewage treatment plant, etc., raw water to be treated is stored in a sedimentation tank to precipitate solids, and then this raw water is passed upward through a filtration member installed in the sedimentation tank for filtration treatment.

[0003] In relation to this, Patent Document 1 discloses a filtration cassette installed in a sedimentation tank that filters raw water to be treated by flowing it upward. This filtration cassette includes a housing and a filter medium disposed within the housing, and perforated plates (water-permeable plates) that allow the passage of raw water to be treated and block the passage of the filter medium are provided at the lower opening and the upper opening of the housing.

[0004] Further, Patent Document 2 discloses that in a sedimentation pond provided with a filtration section for filtering raw water to be treated, a screen is vertically placed at the outflow section of the filtration section.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The technology according to the present disclosure aims to enable more efficient filtration operation of a treatment tank.

Means for Solving the Problems

[0007] To solve the above problems, the technology of this disclosure employs the following configuration. Specifically, the technology of this disclosure is a filtration cassette installed in a treatment tank for circulating and filtering water to be treated, comprising a housing having side walls and a bottom wall, and a filter material housed within the housing and forming a filtration layer, wherein the side wall includes an inlet wall portion into which the water to be treated flows, and an outlet wall portion located on the opposite side of the inlet wall portion, with the filtration layer in between, through which the water to be treated flows out, and a water-pass prevention portion is provided on at least one of the inlet wall portion and the outlet wall portion, which is a prevention portion installation wall, to prevent the passage of the water to be treated and the filter material, and the water-pass prevention portion is installed in such a manner that it prevents the passage of the water to be treated and the filter material in a region of the prevention portion installation wall from the position of the bottom wall in the vertical direction to at least the position of the lower end of the filtration layer. [Effects of the Invention]

[0008] According to the technology disclosed herein, it becomes possible to perform the filtration operation of the treatment tank more efficiently. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows the configuration of a sedimentation tank 100 equipped with a filtration cassette 50 according to an embodiment. [Figure 2] Figure 2 is a longitudinal cross-sectional view showing the filtration system 200A according to Embodiment 1 in the initial stages of filtration operation. [Figure 3] Figure 3 is a longitudinal cross-sectional view showing the filtration system 200A according to Embodiment 1 during the later stages of filtration operation. [Figure 4] Figure 4 is a longitudinal cross-sectional view showing the filtration system 200A according to Embodiment 1 in aeration washing during a washing operation. [Figure 5] Figure 5 is a diagram illustrating the hardware configuration of the control device 90A according to Embodiment 1. [Figure 6] Figure 6 is a longitudinal cross-sectional view showing the filtration system 200B according to Embodiment 2 in filtration operation. [Figure 7]Figure 7 is a longitudinal cross-sectional view showing the filtration system 200B according to Embodiment 2 in aeration washing during a washing operation. [Figure 8] Figure 8 is a longitudinal cross-sectional view showing the filtration system 200C according to Embodiment 3 in filtration operation. [Figure 9] Figure 9 is a longitudinal cross-sectional view showing the filtration system 200C according to Embodiment 3 in the aeration washing operation. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described below with reference to the drawings. However, this description should not be interpreted as limiting, and will not limit the subject matter described in the claims. Furthermore, various changes, substitutions, and modifications can be made without departing from the spirit and scope of this disclosure. Different embodiments can also be combined as appropriate.

[0011] The treatment tank to which the filtration cassette and filtration system described herein are installed is not particularly limited, as it is any tank for separating solid matter (suspended matter) from the water to be treated. Specifically, the treatment tank may be, for example, a sedimentation tank for precipitating and removing solid matter contained in the water to be treated in wastewater treatment, and for further filtration treatment of the water from which the solid matter has been removed. This sedimentation tank may be a primary sedimentation tank located upstream of the reaction tank, or a final sedimentation tank located downstream of the reaction tank. The treatment tank may also be, for example, a solid-liquid separation tank that separates, concentrates, recovers, and removes solid matter contained in the water to be treated by utilizing the difference in specific gravity between liquid and solid in industrial water treatment. Below, as an example of a treatment tank, a case in which the filtration cassette and filtration system described herein are installed in a sedimentation tank in wastewater treatment will be explained.

[0012] [Sedimentation tank 100] First, the overall configuration of the sedimentation tank 100 common to each embodiment (Embodiments 1 to 3) will be described. The sedimentation tank 100 is an example of a filtration device equipped with a filtration cassette and filtration system according to the embodiment.

[0013] The sedimentation tank 100 constitutes part of a water treatment system that treats water to be treated (e.g., sewage), for example, as a sedimentation tank exemplified by a primary sedimentation tank or a final sedimentation tank. This water treatment system includes, for example, a primary sedimentation tank that separates solid components such as pollutants (e.g., solid organic matter) contained in the water to be treated by sedimentation; a reaction tank provided downstream of the primary sedimentation tank that treats the water to be treated by biological treatment such as the standard activated sludge method; a final sedimentation tank provided downstream of the reaction tank that separates solid components such as activated sludge contained in the water to be treated by sedimentation; a concentration device that concentrates the pollutants (primary sludge) separated by sedimentation in the primary sedimentation tank and the activated sludge (excess sludge) separated by sedimentation in the final sedimentation tank; and a digester that biologically treats the organic components contained in the primary sludge and excess sludge supplied from the concentration device using anaerobic bacteria.

[0014] [Overall structure] Figure 1 shows the configuration of a sedimentation tank 100 equipped with a filtration cassette according to an embodiment. Figure 1(A) is a top view of the sedimentation tank 100, Figure 1(B) is a longitudinal cross-sectional view of the sedimentation tank 100 showing a cross-section along line AA in Figure 1(A), and Figure 1(C) is a longitudinal cross-sectional view of the sedimentation tank 100 showing a cross-section along line BB in Figure 1(A). Here, the sedimentation tank 100 is configured such that the water to be treated flows in from the upstream side and flows toward the downstream side. Hereinafter, the direction in which the water to be treated flows in the sedimentation tank 100 will be referred to as the "flow direction" and denoted by the symbol L. The depth direction (i.e., the vertical direction) of the sedimentation tank 100 will be referred to as the "up and down direction" and denoted by the symbol V. The direction perpendicular to the flow direction L and the up and down direction V will be referred to as the "width direction" and denoted by the symbol H. Therefore, Figure 1(B) shows a cross-section perpendicular to the width direction H, and Figure 1(C) shows a cross-section perpendicular to the flow direction L. Furthermore, the flow direction L, vertical direction V, and width direction H will have the same meanings in the description of the filtration cassette 50 described later.

[0015] As shown in FIG. 1(A), the sedimentation tank 100 includes, for example, a sedimentation basin 10 for storing the water to be treated, and a filtration cassette 50 installed in the sedimentation basin 10 for circulating and filtering the water to be treated. The sedimentation tank 100, for example, causes relatively coarse solids contained in the water to be treated flowing into the sedimentation basin 10 to settle in the sedimentation basin 10 by gravitational sedimentation, and further separates relatively fine solids by filtering the water to be treated with the filtration cassette 50. The water to be treated from which solids have been filtered and separated by the filtration cassette 50 (hereinafter also referred to as "filtered water") is discharged to, for example, subsequent equipment. Specifically, when the sedimentation tank 100 is the first sedimentation tank, the water to be treated is discharged to the reaction tank by, for example, a pump or the like. When the sedimentation tank 100 is the final sedimentation tank, the water to be treated is discharged to, for example, a sterilization treatment device (not shown). Thereafter, the sterilization treatment device sterilizes, for example, the water to be treated discharged from the final sedimentation tank, and discharges the sterilized treated water into a river or the like.

[0016] The sedimentation basin 10 is an example of a treatment tank according to the present disclosure. For example, the sedimentation basin 10 is a cross-flow sedimentation basin that retains the water to be treated flowing into the sedimentation basin 10 and separates the solids contained in the water to be treated by sedimenting them by gravitational sedimentation. The water to be treated flows into the sedimentation basin 10 from the upstream side in the flow direction L, for example, and flows toward the downstream side. The sedimentation basin 10 is formed in a substantially rectangular parallelepiped shape having a bottom 10a and side walls 10b, for example, and the longitudinal direction of the sedimentation basin 10 coincides with the flow direction L of the water to be treated. That is, the water to be treated flows along the longitudinal direction of the sedimentation basin 10, specifically, from the left side to the right side in FIG. 1(A). In a top view, the side wall 10b has a rectangular shape that is long in the flow direction L.

[0017] Also, as shown in FIGS. 1(A) to 1(C), the sedimentation tank 100 includes, for example, a plurality of partition walls that partition the inside of the sedimentation basin 10. The plurality of partition walls includes a plurality of partition plates 20 installed vertically and a plurality of partition plates 30 installed horizontally. By the partition plates 20 and 30, for example, a sedimentation section 110, a filtration section 120, a treatment water flow path 130, and a washing and drainage tank 140 are partitioned inside the sedimentation basin 10.

[0018] In the sedimentation section 110, for example, treated water flows in, and a portion of the solids in the treated water settles by gravity. As shown in Figure 1(B), the sedimentation section 110 is, for example, the area enclosed by the bottom 10a, side walls 10b, and partition plates 20, 30 of the sedimentation tank 10. The sedimentation section 110 is formed in the flow direction L, extending from the upstream side to the downstream side of the sedimentation tank 10. As shown in Figure 1(B), the bottom 10a of the sedimentation tank 10 that constitutes the sedimentation section 110 is formed such that the depth of the sedimentation tank 10 gradually decreases as the flow direction L is directed from the upstream side to the downstream side. A solids discharge pipe 102 equipped with a solids discharge valve 101 is installed at the bottom 10a. For example, by opening the solids discharge valve 101 at all times or at predetermined intervals, the solids that have settled in the sedimentation section 110 are discharged from the sedimentation tank 10 via the solids discharge pipe 102 and supplied to downstream equipment (for example, a concentration device).

[0019] The filtration section 120 filters the treated water, from which some of the solids have been separated by the sedimentation section 110, using a filtration cassette 50. As shown in Figures 1(A) to 1(C), the filtration section 120 is a rectangular parallelepiped region defined, for example, by the partition plate 20 and the side surface of the filtration cassette 50. As shown in Figure 1(B), for example, the filtration section 120 is adjacent to the upper region of the sedimentation section 110 on the downstream side in the flow direction L, and adjacent to the upper side of the downstream region of the sedimentation section 110. The lower surface of the filtration section 120 is open to the sedimentation section 110, except for the bottom of the filtration cassette 50. In other words, the bottom of the filtration cassette 50 is closed.

[0020] In the filtration section 120, for example, multiple rectangular prism-shaped filtration cassettes 50 are arranged in parallel. Specifically, as shown in Figure 1(A), for example, two filtration cassettes 50 are arranged with a gap in the width direction H. This creates an inflow region A10 between the two filtration cassettes 50, which is the area into which the water to be treated flows from the sedimentation section 110. The water to be treated flows upward from the downstream region of the sedimentation section 110 into the inflow region A10 of the filtration section 120. In addition, a partition plate 20 between the filtration section 120 and the sedimentation section 110 prevents the water to be treated from overflowing the sedimentation section 110 and flowing into the filtration section 120. In the example shown in Figure 1(A), the sedimentation section 110 and the inflow region A10 are separated by a partition plate 20, but it is not necessary to install a partition plate 20 between the sedimentation section 110 and the inflow region A10. The partition plate 20 only needs to be installed in such a way that it prevents the water to be treated from flowing downstream of the filtration cassette 50 without passing through it. For example, to prevent the water to be treated from flowing downstream (to the treated water flow path 130) over the filtration cassette 50 from the sedimentation section 110 or the inflow area A10, a partition plate 20 extending upward from the side wall of the filtration cassette 50 may be installed. Furthermore, the number and shape of the filtration cassettes 50 arranged in the filtration section 120 are not particularly limited.

[0021] The filtration cassette 50 is installed, for example, in the sedimentation tank 10 and configured to filter the water to be treated by passing through it. The filtration cassette 50 is installed in the filtration section 120, for example, immersed in the water to be treated. The water to be treated that flows from the downstream region of the sedimentation section 110 into the inflow region A10 of the filtration section 120 passes through the filtration cassette 50 laterally (horizontally, and in this embodiment, for example, in the width direction H) by lateral flow. The water to be treated (filtered water) from which the solids have been separated by the filtration cassette 50 flows into the treated water flow path 130 adjacent to the filtration section 120.

[0022] Hereinafter, as will be explained in detail later, the housing 1 of the filtration cassette 50 contains a filter material 2 for filtering the water to be treated (see Figure 2). In the sedimentation tank 100, for example, under normal circumstances, the water to be treated is filtered by the filtration cassette 50, and at predetermined intervals, or when the solid-liquid separation performance of the filter material 2 deteriorates, the filtration of the water to be treated is temporarily stopped and the filter material 2 is washed. Hereinafter, in the sedimentation tank 100, the operation of filtering the water to be treated will be referred to as the "filtration operation," and the operation of washing the filter material 2 will be referred to as the "washing operation."

[0023] As shown in Figure 1(B), the sedimentation tank 100 is equipped with, for example, an aeration cleaning mechanism 60 for performing a cleaning operation. The aeration cleaning mechanism 60 includes, for example, a blower 601 for supplying air and an air cleaning pipe 602 connected to the blower 601. The air outlet of the air cleaning pipe 602 is inserted into the filter cassette 50, and the air supplied from the blower 601 is sent into the filter cassette 50 via the air cleaning pipe 602. The aeration cleaning mechanism 60 generates a swirling flow in the filter cassette 50 by aeration, thereby agitating and cleaning the filter material 2. The treated water containing solids (hereinafter also referred to as "cleaning wastewater") generated during the cleaning operation by the aeration cleaning mechanism 60 flows into the treated water flow path 130.

[0024] The treated water channel 130 carries the treated water (filtered water and washing wastewater) that flows in from the filtration section 120. As shown in Figure 1(B), the treated water channel 130 is formed to sandwich the filtration section 120 and the washing wastewater tank 140 in the width direction H. More specifically, the treated water channel 130 has a pair of troughs 130a, 130a that extend in the flow direction L and are arranged adjacent to (i.e., sandwiching) the filtration section 120 and the washing wastewater tank 140 on both sides in the width direction H. As shown in Figure 1(C), the treated water channel 130 is formed in a trough shape by, for example, the side wall 10b of the sedimentation tank 10 and the partition plate 30. The top surface of the treated water channel 130 is open, and the bottom surface is closed by the partition plate 30.

[0025] The water to be treated flows from the filtration section 120 into the treated water channel 130, and flows from the upstream side to the downstream side in the flow direction L. As shown in Figure 1(A), for example, a treated water withdrawal valve 70 is provided at the downstream end of the treated water channel 130 to open and close the downstream opening of the treated water channel 130. In addition, an outlet 150 is provided between the pair of troughs 130a, 130a and the washing drainage tank 140, for example, to discharge the washing drainage generated during the washing operation into the washing drainage tank 140. Therefore, during filtration operation, by keeping the treated water withdrawal valve 70 open, the filtered water flowing from the filtration section 120 into the treated water channel 130 flows out through the downstream opening of the treated water channel 130 to the downstream equipment of the sedimentation tank 100 (for example, a sterilization treatment device). At this time, a portion of the filtered water may also flow out into the washing drainage tank 140 through the outlet 150. On the other hand, during the washing operation, by keeping the treated water withdrawal valve 70 closed, the washing wastewater does not flow out of the sedimentation tank 100 but flows through the outlet 150 into the washing wastewater tank 140. In the diagrams described below (Figure 1(A), Figures 2-4, Figures 6-9), the white outlined treated water withdrawal valve 70 indicates the valve in the open state (hereinafter also referred to as the open state), and the black outlined treated water withdrawal valve 70 indicates the valve in the closed state (hereinafter also referred to as the closed state).

[0026] The washing wastewater tank 140 stores, for example, washing wastewater that flows in from the treated water channel 130. As shown in Figure 1(B), the washing wastewater tank 140 is adjacent to the downstream side of the filtration section 120 in the flow direction L, and adjacent to the upper side of the downstream region of the sedimentation section 110. The washing wastewater tank 140 is formed, for example, by the side wall 10b of the sedimentation tank 10 and the partition plates 20 and 30. The top surface of the washing wastewater tank 140 is open, and the bottom surface is closed by the partition plate 30.

[0027] Here, the sedimentation tank 100 includes, for example, a return mechanism 80 that returns the washing wastewater stored in the washing wastewater tank 140 to an area upstream of the filtration unit 120. The return mechanism 80 includes, for example, a pump 801 installed in the washing wastewater tank 140 and a return line 802 that transfers the discharged water from the pump 801. The return mechanism 80 returns the washing wastewater to, for example, the sedimentation unit 110 or equipment upstream of the sedimentation tank 100 (for example, an inflow channel to the sedimentation tank 100).

[0028] Furthermore, as shown in Figure 1(C), the sedimentation tank 100 is equipped with a water level gauge S1, for example, which measures the water level on the inlet side of the filtration cassette 50. The water level gauge S1 is an example of a "measuring device" according to this disclosure.

[0029] Here, the inflow water level refers to, for example, the water level of the water to be treated flowing into the filtration cassette 50, and more specifically, the height of the water surface of the water to be treated in the area directly upstream of the filtration cassette 50, that is, the area in which the water to be treated flows into the filtration cassette 50. The outflow water level refers to the water level of the water to be treated that has flowed out of the filtration cassette 50, and more specifically, the height of the water surface of the water to be treated in the area directly downstream of the filtration cassette 50, that is, the area in which the water to be treated flows out of the filtration cassette 50. For example, in this embodiment, the inflow water level of the filtration cassette 50 is the water level of the water to be treated in the inflow area A10, which is the area directly upstream of the filtration cassette 50. Also, for example, in this embodiment, the outflow water level of the filtration cassette 50 is the water level of the water to be treated in the treated water channel 130, which is the area directly downstream of the filtration cassette 50. Therefore, the water level meter S1 measures, for example, the height of the water surface WS in the inflow area A10 of the sedimentation tank 10.

[0030] Furthermore, as shown in Figure 1(C), the sedimentation tank 100 includes a control device 90 that controls, for example, the filtration cassette 50, the aeration and washing mechanism 60, the treated water withdrawal valve 70, and the return mechanism 80. Details of the control device 90 will be described later.

[0031] Hereinafter, the configuration of the sedimentation tank 100 that includes the filtration cassette 50, aeration and cleaning mechanism 60, treated water withdrawal valve 70, return mechanism 80, control device 90, and water level gauge S1 will also be referred to as the filtration system 200.

[0032] [Filtration operation] The filtration operation of the sedimentation tank 100 will be described below. The filtration operation is performed with the water to be treated continuously flowing into the sedimentation section 110 and the treated water withdrawal valve 70 of the treated water channel 130 open.

[0033] In the filtration operation, first, relatively coarse solids contained in the water to be treated that flows into the sedimentation section 110 are separated by sedimentation in the sedimentation section 110. Then, the water from which the solids have been separated flows upward into the inlet area A10 of the filtration section 120. The water to be treated that flows into the inlet area A10 flows into the filtration cassette 50 and passes through the filtration cassette 50 laterally by lateral flow. As the water to be treated passes through the filtration cassette 50, relatively fine solids are filtered and separated.

[0034] The water to be treated (i.e., filtered water) that has passed through the filtration cassette 50 flows into the treated water channel 130 adjacent to the filtration cassette 50 in the width direction H. The filtered water that has flowed into the treated water channel 130 then flows out to the outside of the sedimentation tank 100 through the downstream opening of the treated water channel 130.

[0035] At the start of the filtration operation, the water level on the inlet side and the water level on the outlet side of the filtration cassette 50 are approximately equal. However, as time passes, the water flow resistance of the filtration cassette 50 increases, causing the water level on the inlet side of the filtration cassette 50 to rise and become higher than the water level on the outlet side. For example, after a certain period of time has elapsed since the start of the filtration operation, or when the difference in water levels between the inlet and outlet sides of the filtration cassette 50 exceeds a predetermined level, the system switches to a washing operation.

[0036] [Washing operation] The cleaning operation of the sedimentation tank 100 will be described below. The cleaning operation includes an aeration cleaning process and a rinse cleaning process.

[0037] In the washing operation, aeration washing is performed first. In the aeration washing process, the treated water withdrawal valve 70 of the treated water flow path 130 is closed to stop the outflow of treated water from the sedimentation tank 100 to the outside. By stopping the outflow of treated water, the water level difference between the inlet and outlet sides of the filtration cassette 50 is eliminated, and the inflow of treated water into the sedimentation tank 100 is stopped.

[0038] In this state, the blower 601 of the aeration cleaning mechanism 60 is driven to send air into the filter cassette 50 via the air cleaning pipe 602, aerating the air and creating a swirling flow. The swirling flow causes the filter material 2 inside the filter cassette 50 to flow, and the filter material 2 comes into contact with each other and rubs against each other, thus cleaning the filter material 2. As a result, any solid matter that was trapped in the filter material 2 is detached from the filter material 2 and resuspended in the cleaning wastewater.

[0039] The washing wastewater generated by aeration flows into the treated water channel 130 adjacent to the filtration section 120. The washing wastewater that flows into the treated water channel 130 then flows into the washing wastewater tank 140 through the outlet 150.

[0040] Furthermore, during aeration cleaning, the pump 801 of the return mechanism 80 is driven to return the treated water (cleaning wastewater). Specifically, the cleaning wastewater that flows into the cleaning wastewater tank 140 is sucked up by the pump 801 and returned upstream of the filtration section 120 via the return line 802. As a result, the treated water continuously passes through the filtration cassette 50 during aeration cleaning.

[0041] After performing aeration cleaning for a predetermined period of time, the aeration cleaning is terminated by stopping the blower 601.

[0042] In the washing operation, a rinse wash is performed next. During the rinse wash process, the blower 601 is stopped and the treated water withdrawal valve 70 is closed, while the return mechanism 80 continues to return the treated water (washing wastewater). Even during the rinse wash, the treated water that flows from the sedimentation section 110 into the inflow area A10 of the filtration section 120 passes continuously through the filtration cassette 50 by lateral flow and flows into the washing wastewater tank 140 via the treated water flow path 130. The treated water that flows into the washing wastewater tank 140 is returned upstream of the filtration section 120 by the pump 801. By continuing the rinse wash, the washing wastewater is flushed out by the filtered water, and the treated water beyond the filtration section 120 is gradually purified.

[0043] The rinse cleaning is terminated by stopping the pump 801 after a predetermined time has elapsed since the start of the rinse cleaning, specifically, for example, after a predetermined time has elapsed since the start of the pump 801 operation or after a predetermined time has elapsed since the stop of the blower 601. The stopping of the pump 801 may also be based on the water quality of the cleaning wastewater measured by a water quality sensor (not shown). For example, a turbidimeter may be installed in the return line 802, and the pump 801 may be stopped when the turbidity of the cleaning wastewater falls below a predetermined value (for example, equivalent to filtered water).

[0044] Once the rinsing is complete, the treated water withdrawal valve 70 is opened to restart the filtration operation. As described above, in the sedimentation tank 100, the filtration operation is temporarily stopped and the washing operation is performed.

[0045] [Draining water] For example, for periodic cleaning of the sedimentation tank 100 and the filter cassette 50, the treated water is drained from the sedimentation tank 10 while the filter cassette 50 is installed, thereby draining the filter cassette 50 and emptying the water to be treated from within. Alternatively, the filter cassette 50 may be drained by, for example, lifting it out of the sedimentation tank 10.

[0046] [Filtration System 200] The filtration system 200 according to the embodiment includes, for example, a filtration cassette 50, an aeration and cleaning mechanism 60, a treated water withdrawal valve 70, a return mechanism 80, and a water level gauge S1. The configuration of the filtration system 200 according to each embodiment will be described below.

[0047] [Embodiment 1] First, the configuration of the filtration system 200 equipped with the filtration cassette 50 according to Embodiment 1 will be described. Hereinafter, the filtration cassette 50 according to Embodiment 1 will also be referred to as filtration cassette 50A, the control device 90 according to Embodiment 1 will also be referred to as control device 90A, and the filtration system 200 according to Embodiment 1 will also be referred to as filtration system 200A. Figures 2 to 4 are schematic diagrams showing the filtration system 200A according to Embodiment 1. More specifically, Figure 2 is a longitudinal cross-sectional view showing the filtration system 200A according to Embodiment 1 in the initial stages of filtration operation, Figure 3 is a longitudinal cross-sectional view showing the filtration system 200A according to Embodiment 1 in the later stages of filtration operation, and Figure 4 is a longitudinal cross-sectional view showing the filtration system 200A according to Embodiment 1 during aeration washing in washing operation. In Figures 2 to 4, cross-sections perpendicular to the flow direction L are shown. Note that in Figures 2 to 4, for convenience, the treated water withdrawal valve 70 and the outlet 150 are shown, and the return mechanism 80 is not shown.

[0048] As shown in Figure 2, during filtration operation, the water to be treated that flows into the inlet area A10 of the filtration unit 120 passes through the filtration cassette 50A laterally by lateral flow and flows into the treated water flow path 130. Hereinafter, the direction in which the water to be treated flows through the filtration cassette 50 (50A) will be referred to as the filtration direction D1. In the example shown in Figure 2, the filtration direction D1 is the direction in the width direction H, from the left side (upstream side) to the right side (downstream side).

[0049] [Filtration Cassette 50A] As shown in Figure 2, for example, the filtration cassette 50A is positioned between the inlet area A10 of the filtration section 120 in the sedimentation tank 100 and the treated water flow path 130 in the filtration direction D1. More specifically, the filtration cassette 50A is positioned adjacent to the downstream side of the inlet area A10 and adjacent to the upstream side of the treated water flow path 130 in the filtration direction D1. The filtration cassette 50A comprises, for example, a housing 1 and a filter material 2.

[0050] [Cabinet 1] The housing 1 is a container into which the water to be treated is supplied and filtered. The housing 1 is formed, for example, in the shape of a box with a rectangular horizontal cross-section. However, the shape of the housing 1 is not particularly limited, and for example, it may be a cylindrical shape with a circular or elliptical horizontal cross-section.

[0051] As shown in Figure 1(A), the housing 1 has, for example, a rectangular shape when viewed from above, and the filtration cassette 50A is positioned in the sedimentation tank 10 such that the orientation of any two opposing sides of the housing 1 coincides with the flow direction L of the water to be treated. However, the orientation of the filtration cassette 50A is not limited to this.

[0052] As shown in Figure 2, a filtration chamber 1a is defined inside the housing 1, which is a space through which the filter material 2 is housed and the water to be treated flows. Hereinafter, among the walls constituting the housing 1, the wall that defines the side of the filtration chamber 1a will be called the "side wall", the wall that defines the bottom of the filtration chamber 1a will be called the "bottom wall", and the wall that defines the top of the filtration chamber 1a will be called the "top wall". As shown in Figures 2 and 3, the housing 1 has a side wall 11, a bottom wall 12, and a top wall 13.

[0053] As shown in Figure 2, during filtration operation, a filtration layer 2a is formed in the filtration chamber 1a by the filter material 2 accumulated by buoyancy. The filtration layer 2a floats above the bottom wall 12 of the housing 1. Reference numeral 21 in Figure 2 indicates the lower end of the filtration layer 2a.

[0054] Furthermore, as shown in Figure 2, an air cleaning pipe 602 is inserted and positioned inside the housing 1 (filtration chamber 1a) to clean the filter material 2 by blowing air onto it during the cleaning operation. The air outlet 602a of the air cleaning pipe 602 is positioned below the filtration layer 2a.

[0055] [Side wall 11 of enclosure 1] As shown in Figure 2, the side wall 11 of the housing 1 is formed in a cylindrical shape extending in the vertical direction V, for example, and is arranged to surround the side surface of the filtration chamber 1a. More specifically, the side wall 11 is formed in a rectangular cylindrical shape with a square horizontal cross-section.

[0056] As shown in Figure 2, the side wall 11 includes, for example, an inlet wall portion 111A through which the treated water flows out, and an outlet wall portion 112A located on the opposite side of the inlet wall portion 111A, with the filtration layer 2a in between, through which the treated water flows out.

[0057] The inlet wall 111A and the outlet wall 112A are perpendicular to the filtration direction D1 (in this embodiment, the horizontal direction, for example, the width direction H) and are arranged opposite to each other. The inlet wall 111A and the outlet wall 112A are formed, for example, in the vertical direction V, over the entire area of ​​the side wall 11 (i.e., from the upper end to the lower end of the side wall 11).

[0058] Furthermore, of the side walls 11 of the housing 1, for example, the walls excluding the inlet wall 111A and the outlet wall 112A are configured to prevent the passage of the water to be treated and the filter material 2.

[0059] [Inlet wall portion 111A of side wall 11] The inlet wall portion 111A faces, for example, the inlet side of the filtration cassette 50A (i.e., the upstream side in the filtration direction D1) and is adjacent to the inlet region A10 of the filtration section 120.

[0060] The inlet wall 111A is formed by a water-permeable plate 3, which is configured to allow the passage of the water to be treated while preventing the passage of the filter material 2. The water-permeable plate 3 is, for example, arranged perpendicular to the filtration direction D1 and extends in the vertical direction V from the bottom wall 12 to the top wall 13 (i.e., over the entire area of ​​the filtration chamber 1a).

[0061] The water-permeable plate 3 has multiple communication holes formed therein, for example, as inlets for the water to be treated to flow from the outside (inflow area A10) to the inside (filtration chamber 1a) of the housing 1. The multiple communication holes are, for example, through holes that penetrate the water-permeable plate 3 in the thickness direction, and are formed so that the water to be treated can pass through but the filter material 2 cannot. Therefore, the water to be treated is allowed to flow into the inside of the housing 1 through the inflow wall 111A, and the filter material 2 is prevented from flowing out to the outside of the housing 1 through the inflow wall 111A. The inflow wall 111A can, for example, allow the water to be treated to pass through its entire area while preventing the filter material 2 from passing through. As the water-permeable plate 3, for example, a perforated plate such as perforated metal or a mesh plate such as metal mesh can be used.

[0062] As shown in Figure 2 below, the region of the inlet wall 111A from the position of the bottom wall 12 in the vertical direction V to the position of the lower end 21 of the filtration layer 2a is defined as, for example, the non-adjacent region A1. The non-adjacent region A1 is, that is, the region of the inlet wall 111A below the filtration layer 2a that is not adjacent to (not in contact with) the filtration layer 2a.

[0063] [Outflow wall portion 112A of side wall 11] The outlet wall 112A faces, for example, the outlet side of the filtration cassette 50A (i.e., the downstream side in the filtration direction D1) and is adjacent to the treated water flow path 130.

[0064] For example, a water flow prevention plate 6 is installed in the outflow wall section 112A. Specifically, the outflow wall section 112A has a water flow plate 5 and a water flow prevention plate 6, and the water flow plate 5 and the water flow prevention plate 6 are arranged to overlap in the filtration direction D1. In Embodiment 1, the outflow wall section 112A corresponds to the "prevention section installation wall" according to this disclosure.

[0065] The water-permeable plate 5 is configured, for example, to allow the water to be treated to pass through while preventing the filter material 2 from passing through. The water-permeable plate 5 is arranged, for example, perpendicular to the filtration direction D1 and extends in the vertical direction V from the bottom wall 12 to the top wall 13 (i.e., over the entire area of ​​the filtration chamber 1a). The water-permeable plate 5 has a plurality of communication holes formed therein, for example, as outlets for the water to be treated to flow out from the inside of the housing 1 (filtration chamber 1a) to the outside (treated water flow path 130). The plurality of communication holes are, for example, through holes that penetrate the water-permeable plate 5 in the thickness direction, and are formed so that the water to be treated can pass through but the filter material 2 cannot. Therefore, the water to be treated is allowed to flow out to the outside of the housing 1 through the water-permeable plate 5, while the filter material 2 is prevented from flowing out to the outside of the housing 1 through the water-permeable plate 5. The water-permeable plate 5 is configured, for example, to allow the water to be treated to pass through its entire area while preventing the filter material 2 from passing through. For the water-permeable plate 5, for example, a perforated plate such as punched metal or a mesh plate such as metal mesh can be used.

[0066] The water-blocking plate 6 is configured to prevent, for example, the passage of the water to be treated and the filter material 2. In other words, the water-blocking plate 6 is formed in such a way that the water to be treated and the filter material 2 cannot pass through it. Reference numeral 61 in Figure 2 indicates the upper end of the water-blocking plate 6.

[0067] The water-blocking plate 6 is formed, for example, in the shape of a plate, and is perpendicular to the filtration direction D1 and extends at least upward from the bottom wall 12. Furthermore, the water-blocking plate 6 is positioned so as to overlap with a portion of the water-passing plate 5, including the lower end, in the filtration direction D1. In other words, the water-blocking plate 6 is installed so as to cover a portion of the water-passing plate 5, including the lower end. The water-blocking plate 6 is an example of a "water-blocking section" according to this disclosure. However, the water-blocking section does not have to be in the shape of a plate.

[0068] The water-blocking plate 6 extends, for example, in the vertical direction V from the position of the bottom wall 12 to at least the position of the lower end 21 of the filtration layer 2a. As a result, the water-blocking plate 6 covers the portion of the water-passing plate 5 from the position of the bottom wall 12 in the vertical direction V to at least the position of the lower end 21 of the filtration layer 2a. Therefore, the outflow wall portion 112A is configured to prevent (block) the passage of the water to be treated in the region from the position of the bottom wall 12 in the vertical direction V to at least the position of the lower end 21 of the filtration layer 2a.

[0069] As shown in Figure 2 below, the region of the outflow wall 112A from the position of the bottom wall 12 in the vertical direction V to the position of the lower end 21 of the filtration layer 2a is defined as, for example, the non-adjacent region A3. The non-adjacent region A3 is, that is, the region of the outflow wall 112A below the filtration layer 2a that is not adjacent to (not in contact with) the filtration layer 2a. The length of the non-adjacent region A3 in the vertical direction V (i.e., the length extending upward from the bottom wall 12) changes according to the vertical position of the filtration layer 2a, which changes according to the water level on the inflow side, as will be described later. The water passage prevention plate 6 prevents the passage of treated water in the non-adjacent region A3, which is not adjacent to the filtration layer 2a, by covering the water passage plate 5 in at least the non-adjacent region A3 of the outflow wall 112A.

[0070] Furthermore, the water-blocking plate 6 is installed such that, for example, it does not cover the water-passing plate 5 in at least a portion of the outflow wall portion 112A. In other words, at least a portion of the water-passing plate 5 is not covered by the water-blocking plate 6, allowing the treated water (i.e., filtered water) treated by the filtration layer 2a to pass through.

[0071] As shown in Figure 2 below, the area of ​​the outlet wall 112A where the water-blocking plate 6 (blocking part) is not installed, that is, the area where the water-passing plate 5 is not covered by the water-blocking plate 6 and the water to be treated can pass through, is defined as, for example, the water-passable area A4. The water-passable area A4 is, for example, the area of ​​the outlet wall 112A above the upper end portion 61 of the water-blocking plate 6. Since the water-passable area A4 is the area above the lower end portion 21 of the filtration layer 2a, it is adjacent to the filtration layer 2a. The filtered water flows out from the inside of the housing 1 (filtration chamber 1a) to the outside (treated water flow path 130) through the water-passable area A4 in the outlet wall 112A.

[0072] As described above, the water-blocking plate 6 is installed on the outlet wall 112A such that, for example, it prevents the passage of water to be treated in at least the non-adjacent area A3 of the outlet wall 112A, while a water-passable area A4 through which filtered water can pass is formed on the outlet wall 112A.

[0073] Furthermore, the water-blocking plate 6 is configured to be able to move up and down in the vertical direction V, for example, thereby changing its height from the bottom wall 12. In other words, the amount of protrusion from the bottom wall 12 (the length of the portion extending upward from the bottom wall 12) of the water-blocking plate 6 is adjustable. This allows the water-blocking plate 6 to adjust the area it covers the water-blocking plate 5. As will be described in detail later, the water-blocking plate 6 prevents the passage of treated water in at least the non-adjacent area A3 of the outflow wall 112A by changing its height from the bottom wall 12 according to the vertical position of the filtration layer 2a, for example, under the control of the control device 90A. The height of the water-blocking plate 6 is changed by driving it with a drive source (not shown) controlled by the control device 90A. As a drive source, for example, an air cylinder, hydraulic cylinder, linear actuator, etc. may be used.

[0074] [Bottom wall 12 of enclosure 1] As shown in Figure 2, the bottom wall 12 is formed, for example, in the shape of a plate and is arranged perpendicular to the vertical direction V so as to cover the bottom of the housing 1 (the bottom surface of the filtration chamber 1a). The bottom wall 12 is provided, for example, at the lower end of the side wall 11. However, the bottom wall 12 only needs to be located below the filter material 2, and may be provided in the middle of the side wall 11. If the distance between the bottom wall 12 of the housing 1 and the lower end 21 of the filtration layer 2a is a1, the distance a1 is not particularly limited, but it is preferably 20% or more of the thickness (length in the vertical direction) of the filtration layer 2a, and more preferably 30% or more. The bottom wall 12 is configured to prevent the passage of the water to be treated and the filter material 2. In other words, the bottom wall 12 is formed so that the water to be treated and the filter material 2 cannot pass through. The bottom of the housing 1 (the bottom surface of the filtration chamber 1a) is closed by the bottom wall 12. As shown in Figure 2, the filtration cassette 50A is installed in the sedimentation tank 10 such that, for example, the bottom wall 12 of the housing 1 and the partition plate 30 that constitutes the bottom of the treated water flow path 130 are located in the same plane in the vertical direction V. The bottom wall 12 may also be formed integrally with the partition plate 30, for example.

[0075] [Upper wall 13 of cabinet 1] As shown in Figure 2, the upper wall 13 is formed, for example, in the shape of a plate and is arranged perpendicular to the vertical direction V so as to cover the upper part of the housing 1 (the upper surface of the filtration chamber 1a). The upper wall 13 is provided, for example, at the upper end of the side wall 11. However, the upper wall 13 only needs to be located above the filter material 2, and may be provided in the middle of the side wall 11. The distance between the upper wall 13 of the housing 1 and the upper end of the filtration layer 2a is not particularly limited, but it is preferably 20% or more of the thickness of the filtration layer 2a, and more preferably 30% or more. The upper wall 13 is configured to prevent the passage of the water to be treated and the filter material 2. In other words, the upper wall 13 is formed so that the water to be treated and the filter material 2 cannot pass through it. The upper wall 13 closes the upper part of the housing 1 (the upper surface of the filtration chamber 1a). As shown in Figure 2, the filtration cassette 50A is installed in the sedimentation tank 10 such that, for example, the upper wall 13 of the housing 1 is located above the water surface WS on the inlet side (inlet area A10).

[0076] [Filter material 2] As shown in Figure 2, the housing 1 contains multiple filter media 2. The filter media 2 has, for example, a specific gravity of less than 1, is buoyant of the water to be treated, and has a form that can capture solid matter contained in the water to be treated. As the filter media 2, for example, a cylindrical material made of a resin material such as foamed resin with irregularities on its surface can be used. However, the material and shape of the filter media 2 are not particularly limited.

[0077] During filtration operation, the buoyancy acting on the filter material 2 causes multiple filter materials 2 to accumulate, forming a filtration layer 2a between the inlet wall 111A and the outlet wall 112A in the filtration chamber 1a, as shown in Figure 2. The filtration layer 2a is adjacent to (in contact with) the inlet wall 111A and the outlet wall 112A.

[0078] The filtration layer 2a is configured such that multiple filter materials 2 are packed together, creating fine gaps between them. As the water to be treated passes through these gaps between the filter materials 2 and through the hollow sections of the cylindrical filter materials 2, solid particles contained in the water are trapped on the surface of the filter materials 2.

[0079] During filtration operation, the buoyancy acting on the filter material 2 pushes it upward and causes it to float. As shown in Figure 2, the filtration layer 2a floats above the bottom wall 12 of the housing 1 and is positioned at a distance from the bottom wall 12. At this time, the vertical position of the filtration layer 2a corresponds to the water level on the inflow side, and as the water level on the inflow side changes, the vertical position of the filtration layer 2a also changes. Specifically, as the water level on the inflow side rises, the filtration layer 2a also rises, and as the water level on the inflow side falls, the filtration layer 2a also falls. Since the specific gravity of the filter material 2 is less than 1, a portion of the filtration layer 2a (the upper end) is located above the water surface WS on the inflow side.

[0080] Here, the distance a1 between the bottom wall 12 of the housing 1 and the lower end 21 of the filtration layer 2a is the distance from the position of the bottom wall 12 to the position of the lower end 21 of the filtration layer 2a in the vertical direction V. Therefore, the distance a1 can be said to be equivalent to the length of the non-adjacent region A3 of the outflow wall 112A in the vertical direction V. The distance a1 changes depending on the vertical position of the filtration layer 2a, that is, depending on the water level on the inflow side. The distance a1 can be derived, for example, based on the water level on the inflow side and the thickness of the filtration layer 2a (length in the vertical direction V).

[0081] [Control device 90A] The control device 90A operates the filtration system 200A by controlling, for example, the filtration cassette 50A, the aeration and cleaning mechanism 60, the treated water withdrawal valve 70, and the return mechanism 80.

[0082] Specifically, the control device 90A performs filtration and cleaning operations by controlling, for example, the opening and closing of the treated water withdrawal valve 70, the driving of the blower 601 of the aeration and cleaning mechanism 60, and the driving of the pump 801 of the return mechanism 80.

[0083] Furthermore, during filtration operation in which the water to be treated is filtered by the filtration cassette 50A, the control device 90A controls the height of the water-blocking plate 6 of the outlet wall 112A by, for example, following the vertical position of the filtration layer 2a, thereby preventing the water to be treated from passing through at least the non-adjacent area A3 of the outlet wall 112A.

[0084] Specifically, the control device 90A obtains, for example, the water level on the inlet side of the filtration cassette 50A, measured by the water level gauge S1, from the water level gauge S1. Then, the control device 90A controls the height of the water-blocking plate 6 from the bottom wall 12 by controlling the drive source (not shown) of the water-blocking plate 6 according to the water level on the inlet side of the filtration cassette 50A. More specifically, the control device 90A controls the height of the water-blocking plate 6 from the bottom wall 12 so that it is greater than or equal to the distance a1 between the bottom wall 12 and the filtration layer 2a.

[0085] The control device 90A controls the height of the water-blocking plate 6 to be equal to or greater than the distance a1 between the bottom wall 12 and the filter layer 2a, in accordance with the vertical position of the filter layer 2a. This maintains that the water-passing plate 5 is covered by the water-blocking plate 6 in at least the non-adjacent area A3 of the outlet wall 112A. In other words, even if the vertical position of the filter layer 2a changes according to the water level on the inlet side of the filter cassette 50A, the state in which the passage of water to be treated is prevented in at least the non-adjacent area A3 of the outlet wall 112A is maintained.

[0086] Furthermore, the control device 90A controls the height of the water-blocking plate 6 so that, for example, during filtration operation, the distance between the upper end 61 of the water-blocking plate 6 and the lower end 21 of the filtration layer 2a in the vertical direction V is less than a predetermined threshold (first threshold). The first threshold is set, for example, based on the width of the water-permeable area A4 required in the outlet wall 112A according to the processing amount of liquid to be treated flowing through the filtration cassette 50A during filtration operation. Alternatively, the control device 90A may control the height of the water-blocking plate 6 so that, for example, during filtration operation, the distance between the upper end 61 of the water-blocking plate 6 and the lower end 21 of the filtration layer 2a becomes 0, that is, the height of the water-blocking plate 6 becomes equal to the distance a1 between the bottom wall 12 and the filtration layer 2a (i.e., the vertical positions of the upper end 61 of the water-blocking plate 6 and the lower end 21 of the filtration layer 2a coincide).

[0087] Furthermore, the control device 90A controls the height of the water-blocking plate 6 so that the treated water can pass through an area of ​​the outlet wall 112A that is larger than or equal to a predetermined threshold (second threshold) during aeration cleaning, for example, when air is blown onto the filter material 2 inside the housing 1 to clean the filter material 2. In other words, the control device 90A controls the height of the water-blocking plate 6 so that the area of ​​the water-passable area A4 is larger than or equal to the second threshold. The second threshold is set, for example, based on the area of ​​the water-passable area A4 required in the outlet wall 112A according to the processing volume of the liquid to be treated flowing through the filter cassette 50A during aeration cleaning. The second threshold may also be set, for example, as the ratio of the water-passable area A4 to the entire area of ​​the outlet wall 112A (the area from the bottom wall 12 to the top wall 13). The control device 90A may, for example, as shown in Figure 4, control the height of the water flow prevention plate 6 so that the water to be treated can pass through the entire area of ​​the outlet wall 112A during aeration cleaning, that is, so that the height of the water flow prevention plate 6 becomes 0 and the water flow plate 5 is not covered by the water flow prevention plate 6.

[0088] The control device 90A may, for example, calculate distance a1 based on a measured value of the water level on the inlet side and a preset value for the thickness of the filter layer 2a, and control the height of the water-blocking plate 6 according to the calculated value of distance a1. Alternatively, for example, a preset value for the height of the water-blocking plate 6 may be set in accordance with the water level on the inlet side, and the control device 90A may control the height of the water-blocking plate 6 according to the measured value of the water level on the inlet side and the preset value for the height.

[0089] Figure 5 is a diagram illustrating the hardware configuration of the control device 90A according to Embodiment 1. As shown in Figure 5, the control device 90A is, for example, an electronic device having an electronic circuit. More specifically, the control device 90A is a computer device having, for example, a CPU 901 which is a processor, a memory 902, a communication device 903, and a storage medium 904. Each part is connected to each other via, for example, a bus 905.

[0090] The storage medium 904 has, for example, a program storage area (not shown) for storing a program 610 for operating the filtration system 200A. The storage medium 904 also has, for example, an information storage area 620 for storing information used when operating the filtration system 200A. The storage medium 904 may be, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0091] The CPU 901 controls the operation of the filtration system 200A, for example, by executing a program 210 loaded from the storage medium 904 into the memory 902.

[0092] The communication device 903 accesses, for example, an operating terminal (not shown) where an operator inputs necessary information via a network (not shown), such as the Internet.

[0093] Furthermore, the electronic circuitry of the control device 90A may be, for example, an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The processing for operating the filtration system 200A may also be executed, for example, on the FPGA or ASIC.

[0094] [Filtration operation using Filtration System 200A] The operation of the filtration system 200A during filtration will be described below with reference to Figures 2 and 3.

[0095] As described above, the filtration operation is performed with the water to be treated continuously flowing into the sedimentation section 110 and the treated water withdrawal valve 70 of the treated water channel 130 open.

[0096] As shown in Figure 2, in the initial stages of filtration, for example, the water flow resistance of the filtration cassette 50A is small, so the water level difference between the inlet and outlet sides of the filtration cassette 50A is small. At this time, the filtration layer 2a is slightly floating above the bottom wall 12 of the housing 1, but the water flow prevention plate 6 covers the water flow plate 5 in the non-adjacent region A3 of the outlet wall 112A, thus preventing the water to be treated from passing through the non-adjacent region A3.

[0097] As time elapses since the start of the filtration operation, the water flow resistance of the filtration cassette 50A increases, causing the water level on the inlet side of the filtration cassette 50A to gradually rise. As the water level on the inlet side rises, the filtration layer 2a rises, and the distance a1 between the bottom wall 12 of the housing 1 and the lower end 21 of the filtration layer 2a gradually increases. At this time, the control device 90A raises the water flow prevention plate 6 according to the measured value of the water level on the inlet side obtained from the water level gauge S1, for example, causing the water flow prevention plate 6 to follow the rise of the filtration layer 2a. The control device 90A increases the height of the water flow prevention plate 6 so that the distance is greater than or equal to the distance a1. The height of the water flow prevention plate 6 is adjusted so that, for example, the distance between the upper end 41 of the water flow prevention plate 6 and the lower end 21 of the filtration layer 2a in the vertical direction V is less than a predetermined threshold (first threshold).

[0098] As shown in Figure 3, in the later stages of filtration operation, for example, the difference in water level between the inlet and outlet sides of the filtration cassette 50A becomes large, causing the filtration layer 2a to float significantly above the bottom wall 12 of the housing 1. However, because the control device 90A causes the water-blocking plate 6 to rise in accordance with the filtration layer 2a, even in the later stages of filtration operation, the state in which the water-passing plate 5 is covered by the water-blocking plate 6 in the non-adjacent region A3 of the outlet wall 112A is maintained, and the state in which the water to be treated is prevented from passing through the non-adjacent region A3 is maintained.

[0099] As described above, during filtration operation by the filtration system 200A, even if the vertical position of the filtration layer 2a changes according to the water level on the inlet side of the filtration cassette 50A, the water to be treated is prevented from passing through the non-adjacent region A3 of the outlet wall 112A that is not adjacent to the filtration layer 2a.

[0100] For example, if the water to be treated can pass through the non-adjacent area A3 of the outlet wall 112A, then a portion of the water to be treated flowing through the filtration cassette 50A may flow into the interior of the housing 1 from the non-adjacent area A1 of the inlet wall 111A that is not adjacent to the filtration layer 2a, and without passing through the filtration layer 2a, flow below the filtration layer 2a and out of the housing 1 from the non-adjacent area A3 of the outlet wall 112A. In other words, a short path of the water to be treated may occur. If a short path occurs during filtration operation, there is a risk that a portion of the water to be treated will not be filtered by the filter material 2 and will flow out from the filtration cassette 50A to the downstream side (treated water flow path 130).

[0101] In contrast, during filtration operation by the filtration system 200A, for example, in the outlet wall section 112A, the non-adjacent area A3 that is not adjacent to the filtration layer 2a is blocked by the water-permeability plate 6, while the water-permeable area A4 adjacent to the filtration layer 2a is open to filtered water. Therefore, the water to be treated that flows into the housing 1 of the filtration cassette 50A is filtered by passing through the filtration layer 2a, for example, before reaching the water-permeable area A4 of the outlet wall section 112A, and then flows out from the water-permeable area A4 to the outside of the housing 1 (treated water flow path 130). Consequently, the water to be treated that flows into the housing 1 of the filtration cassette 50A from the non-adjacent area A1 that is not adjacent to the filtration layer 2a in the inlet wall section 111A enters the filtration layer 2a from the lower end 21 of the filtration layer 2a, is filtered by passing through the filtration layer 2a, and then flows out to the outside of the housing 1. In this way, short paths of the water to be treated are prevented during filtration operation by the filtration system 200A.

[0102] [Cleaning operation using filtration system 200A] The operation of the filtration system 200A during the washing operation will be explained below with reference to Figure 4.

[0103] For example, after a certain period of time has elapsed since the start of filtration operation, or when the water level difference between the inlet and outlet sides of the filtration cassette 50A exceeds a predetermined level, the control device 90A closes the treated water withdrawal valve 70 and drives the blower 601 of the aeration cleaning mechanism 60 and the pump 801 of the return mechanism 80 to start aeration cleaning. During aeration cleaning, for example, as shown in Figure 4, the filter material 2 flows due to the swirling flow generated inside the housing 1 (filtration chamber 1a) of the filtration cassette 50A, and the filter material 2 spreads throughout the entire housing 1.

[0104] Here, at the start of aeration cleaning, the control device 90A may temporarily block more than half of the area of ​​the outlet wall 112A by adjusting the height of the water-blocking plate 6 of the outlet wall 112A. Specifically, for example, the control device 90A may adjust the height of the water-blocking plate 6 so that more than half of the area of ​​the water-passing plate 5 is covered by the water-blocking plate 6. In this case, the entire area of ​​the outlet wall 112A may be blocked by the water-blocking plate 6. By blocking more than half or the entire area of ​​the outlet wall 112A at the start of aeration cleaning and suppressing the outflow of cleaning wastewater (treated water), complete mixing of the filter material 2 by swirling flow is promoted, and sludge attached to the filter material 2 becomes easier to remove.

[0105] For example, after a certain period of time has elapsed since the start of aeration cleaning, the control device 90A lowers the water-blocking plate 6, for example as shown in Figure 4, allowing the treated water to pass through part or all of the outlet wall 112A, thereby discharging (flowing out) the cleaning wastewater from inside the housing 1 of the filtration cassette 50A into the treated water flow path 130. The control device 90A lowers the water-blocking plate 6, for example, so that the width of the water-permeable area A4 is greater than or equal to a predetermined threshold (second threshold). In Figure 4, as an example, the height of the water-blocking plate 6 is adjusted so that the treated water can pass through the entire outlet wall 112A, that is, so that the entire outlet wall 112A becomes the water-permeable area A4. By allowing the treated water to pass through the entire outlet wall 112A, the water flow resistance of the filtration cassette 50A is reduced, making it possible to smoothly discharge the cleaning wastewater generated inside the housing 1.

[0106] As shown in Figure 4, during aeration washing, the dispersion of the filter material 2 reduces the water flow resistance of the filter cassette 50A, and the closing of the treated water withdrawal valve 70 causes the water level in the treated water channel 130 to rise. As a result, the washing wastewater flowing into the treated water channel 130 flows through the outlet 150 into the washing wastewater tank 140. The washing wastewater flowing into the washing wastewater tank 140 is sucked up by the pump 801 of the return mechanism 80 and returned upstream of the filtration section 120 via the return line 802.

[0107] After performing aeration cleaning for a predetermined time, the control device 90A terminates the aeration cleaning by stopping the blower 601 and starts rinsing cleaning by continuing to return the cleaning wastewater with the pump 801.

[0108] After a predetermined time has elapsed since the start of the rinse cleaning, the control device 90A terminates the rinse cleaning by stopping the pump 801 and restarts the filtration operation by opening the treated water withdrawal valve 70.

[0109] [Effects and Effects of Embodiment 1] As described above, the filtration cassette 50A according to Embodiment 1 comprises a housing 1 having side walls 11 and a bottom wall 12, and a filter material 2 housed within the housing 1 and forming a filtration layer 2a. The side wall 11 includes an inlet wall portion 111A into which the water to be treated flows, and an outlet wall portion 112A located on the opposite side of the inlet wall portion 111A, with the filtration layer 2a in between, through which the water to be treated flows out. The outlet wall portion 112A (wall where the prevention part is installed) is provided with a water-permeability prevention plate 6 that prevents the passage of the water to be treated and the filter material 2. The water-permeability prevention plate 6 is installed in the outlet wall portion 112A such that it prevents the passage of the water to be treated and the filter material 2 in the area from the position of the bottom wall 12 in the vertical direction to at least the position of the lower end 21 of the filtration layer 2a.

[0110] As described above, the filtration cassette 50A allows the water to be treated to flow into the housing 1 from the inlet wall portion 111A, which is part of the side wall 11, and to flow out of the housing 1 from the outlet wall portion 112A. In other words, the filtration cassette 50A has inlet and outlet ports for circulating the water to be treated on the side of the housing 1. Therefore, for example, the inlet and outlet ports (inlet wall portion 111A and outlet wall portion 112A) can be cleaned from above the water surface during filtration operation without having to lift the filtration cassette 50A out of the sedimentation tank 10. On the other hand, for example, if a screen (water-permeable plate) for circulating the water to be treated is installed at the bottom of the housing, cleaning the screen would require stopping the filtration operation, draining the treated water from the sedimentation tank 10, or lifting the filtration cassette 50A out of the sedimentation tank 10. In comparison to this, since the filtration cassette 50A allows cleaning of the inlet and outlet ports during filtration operation as described above, the number of times the filtration operation needs to be stopped for cleaning can be reduced. This makes it possible to perform continuous filtration operation for a long period of time. As a result, the filtration operation of sedimentation tank 100 can be performed more efficiently.

[0111] Furthermore, with the filtration cassette 50A configured as described above, the passage of water to be treated is prevented in the non-adjacent region A3 of the outflow wall 112A that is not adjacent to the filtration layer 2a, thereby preventing short-circuiting of the water to be treated and enabling effective filtration of the water to be treated. As a result, filtration operation can be performed more efficiently.

[0112] Furthermore, the filtration system 200A according to Embodiment 1 includes a control device 90A that controls the height of the water flow prevention plate 6 in accordance with the vertical position of the filtration layer 2a. This prevents the passage of treated water through non-adjacent areas A3 that are not adjacent to the filtration layer 2a in the outlet wall 112A, even if the vertical position of the filtration layer 2a changes during filtration operation, thereby preventing short-circuiting of the treated water.

[0113] Furthermore, the filtration system 200A according to Embodiment 1 further includes a water level gauge S1 for measuring the water level on the inlet side of the filtration cassette 50A, and the control device 90A controls the height of the water-blocking plate 6 according to the water level on the inlet side. This makes it possible to adjust the height of the water-blocking plate 6 to follow the change in the vertical position of the filtration layer 2a in response to the change in the water level on the inlet side.

[0114] Furthermore, the control device 90A according to Embodiment 1 controls the height of the water-blocking plate 6 in accordance with the vertical position of the filter layer 2a during filtration operation in which the water to be treated is filtered by the filter cassette 50A, and controls the height of the water-blocking plate 6 during cleaning operation in which air is blown onto the filter material 2 inside the housing 1 to clean the filter material 2, so that the water to be treated can pass through an area of ​​the outlet wall 112A that is wider than or equal to a threshold. This prevents short-circuiting of the water to be treated during filtration operation, while also allowing for the smooth discharge of cleaning wastewater generated inside the housing 1 during cleaning operation.

[0115] In this embodiment, the water-blocking plate 6 is configured to allow adjustment of its height from the bottom wall 12, but this disclosure is not limited thereto. For example, the height of the water-blocking plate 6 may be fixed. In that case, the height of the water-blocking plate 6 may be set to be greater than or equal to the maximum value of the distance a1 between the bottom wall 12 of the housing 1 and the lower end 21 of the filter layer 2a when the water level on the inlet side is at its maximum during filtration operation. This prevents the passage of water to be treated in non-adjacent areas A3 that are not adjacent to the filter layer 2a in the outlet wall 112A, even when the filter layer 2a has floated to its highest position during filtration operation, thereby preventing short-circuiting of the water to be treated.

[0116] [Embodiment 2] Next, the configuration of the filtration system 200 equipped with the filtration cassette 50 according to Embodiment 2 will be described. Hereinafter, the filtration cassette 50 according to Embodiment 2 will also be referred to as the filtration cassette 50B, the control device 90 according to Embodiment 2 will also be referred to as the control device 90B, and the filtration system 200 according to Embodiment 2 will also be referred to as the filtration system 200B. In the following description of Embodiment 2, the differences from Embodiment 1 will be the main focus, and components similar to those in Embodiment 1 will be denoted by the same reference numerals, thus omitting detailed explanations. Figures 6 and 7 are schematic diagrams showing the filtration system 200B according to Embodiment 2. More specifically, Figure 6 is a longitudinal cross-sectional view showing the filtration system 200B according to Embodiment 2 during filtration operation (for example, the later stages of filtration operation), and Figure 7 is a longitudinal cross-sectional view showing the filtration system 200B according to Embodiment 2 during aeration washing during washing operation. Note that in Figures 6 and 7, for convenience, the treated water withdrawal valve 70 and the outlet 150 are shown, and the return mechanism 80 is not shown.

[0117] [Filtration Cassette 50B] As shown in Figure 6, the filtration cassette 50B according to Embodiment 2 differs from Embodiment 1 in that, for example, the water flow prevention plate (prevention part) is installed on the inlet wall rather than the outlet wall.

[0118] Specifically, the inlet wall portion 111B of the filtration cassette 50B has a water-passing plate 3 as described in Embodiment 1, as well as a water-blocking plate 4, and the water-passing plate 3 and the water-blocking plate 4 are arranged to overlap in the filtration direction D1. In Embodiment 2, the inlet wall portion 111B corresponds to the "blocking section installation wall" according to this disclosure.

[0119] The water-blocking plate 4 is configured to prevent the passage of the water to be treated and the filter material 2, similar to the water-blocking plate 6 in Embodiment 1. In other words, the water-blocking plate 4 is formed in such a way that the water to be treated and the filter material 2 cannot pass through. Reference numeral 41 in Figure 6 indicates the upper end of the water-blocking plate 4.

[0120] The water-blocking plate 4 is formed, for example, in the shape of a plate, and is perpendicular to the filtration direction D1 and extends at least upward from the bottom wall 12. The water-blocking plate 4 is an example of a "water-blocking section" according to this disclosure.

[0121] The water-blocking plate 4 extends, for example, in the vertical direction V from the position of the bottom wall 12 to at least the position of the lower end 21 of the filtration layer 2a. As a result, the water-blocking plate 4 covers the portion of the water-passing plate 3 from the position of the bottom wall 12 in the vertical direction V to at least the position of the lower end 21 of the filtration layer 2a. In other words, the water-blocking plate 4 covers the water-passing plate 3 in at least the non-adjacent region A1. As a result, the water-blocking plate 4 prevents the passage of water to be treated in the non-adjacent region A1 of the inlet wall portion 111B that is not adjacent to the filtration layer 2a. In addition, at least a portion of the water-passing plate 3 is not covered by the water-blocking plate 4 and is able to allow water to be treated to pass through.

[0122] As shown in Figure 6 below, the area of ​​the inlet wall 111B through which the water to be treated can pass without the water-blocking plate 4 (blocking part) being installed is defined as, for example, the water-passable area A2. The water-passable area A2 is, for example, the area of ​​the inlet wall 111B above the upper end portion 41 of the water-blocking plate 4. Since the water-passable area A2 is the area above the lower end portion 21 of the filtration layer 2a, it is adjacent to the filtration layer 2a. The water to be treated flows from the outside of the housing 1 (inlet area A10) to the inside (filtration chamber 1a) through the water-passable area A2 in the inlet wall 111B.

[0123] As described above, the water-blocking plate 4 is installed on the inlet wall 111B such that, for example, it prevents the passage of the water to be treated in at least the non-adjacent area A1 of the inlet wall 111B, while a water-passable area A2 through which the water to be treated can pass is formed on the inlet wall 111B.

[0124] Furthermore, the water-blocking plate 4 is configured to be able to move up and down in the vertical direction V, for example, thereby allowing its height from the bottom wall 12 to be changed. In other words, the amount of protrusion from the bottom wall 12 (the length of the portion extending upward from the bottom wall 12) of the water-blocking plate 4 is adjustable. This allows the water-blocking plate 4 to adjust the area it covers the water-blocking plate 3. The height of the water-blocking plate 4 is changed by driving it with a drive source (not shown) controlled by the control device 90B, for example. As the drive source, an air cylinder, hydraulic cylinder, linear actuator, etc., may be used.

[0125] As shown in Figure 6, the outflow wall portion 112B according to Embodiment 2 does not have the water flow prevention plate 6 described above, for example, and is formed by the water flow plate 5 described in Embodiment 1.

[0126] [Control device 90B] The control device 90B according to Embodiment 2 prevents the passage of water to be treated in at least the non-adjacent region A1 of the inlet wall 111B by, for example, controlling the height of the water-blocking plate 4 of the inlet wall 111B in accordance with the vertical position of the filtration layer 2a during filtration operation.

[0127] Specifically, the control device 90B controls the height of the water-blocking plate 4 from the bottom wall 12 by controlling the drive source (not shown) of the water-blocking plate 4 according to the water level on the inlet side of the filtration cassette 50B obtained from the water level gauge S1. For example, the control device 90B controls the height of the water-blocking plate 4 from the bottom wall 12 so that it is greater than or equal to the distance a1 between the bottom wall 12 and the filtration layer 2a.

[0128] The control device 90B controls the height of the water-blocking plate 4, so that even if the vertical position of the filtration layer 2a changes according to the water level on the inlet side of the filtration cassette 50B, the state in which the passage of water to be treated is prevented in at least the non-adjacent region A1 of the inlet wall 111B is maintained.

[0129] Furthermore, the control device 90B controls the height of the water-blocking plate 4 so that, for example, during filtration operation, the distance between the upper end 41 of the water-blocking plate 4 and the lower end 21 of the filtration layer 2a in the vertical direction V is less than a predetermined threshold (third threshold). The third threshold is set, for example, based on the width of the water-permeable area A2 required in the inlet wall 111B according to the processing amount of liquid to be treated flowing through the filtration cassette 50B during filtration operation. Alternatively, the control device 90B may control the height of the water-blocking plate 4 so that its height is equal to the distance a1 between the bottom wall 12 and the filtration layer 2a (that is, so that the vertical positions of the upper end 41 of the water-blocking plate 4 and the lower end 21 of the filtration layer 2a coincide).

[0130] Furthermore, the control device 90B controls the height of the water-blocking plate 4 so that, for example, during aeration washing in a washing operation, the water to be treated can pass through an area of ​​the inlet wall 111B that is larger than or equal to a predetermined threshold (fourth threshold). In other words, the control device 90B controls the height of the water-blocking plate 4 so that the area of ​​the water-passable area A2 is larger than or equal to the fourth threshold. The fourth threshold is set, for example, based on the area of ​​the water-passable area A4 required in the inlet wall 111B according to the processing amount of the liquid to be treated flowing through the filter cassette 50B during aeration washing. The fourth threshold may also be set, for example, as the ratio of the water-passable area A2 to the entire area of ​​the inlet wall 111B (the area from the bottom wall 12 to the top wall 13). The control device 90B may also control the height of the water-blocking plate 4 so that, for example, during washing operation, the water to be treated can pass through the entire area of ​​the inlet wall 111B.

[0131] The control device 90B may, for example, control the height of the water-blocking plate 4 according to a calculated distance a1 based on the measured water level on the inlet side and the set value of the thickness of the filter layer 2a. Alternatively, the control device 90B may control the height of the water-blocking plate 4 according to the measured water level on the inlet side and a preset height setting.

[0132] [Filtration operation using Filtration System 200B] As shown in Figure 6, during filtration operation using the filtration system 200B according to Embodiment 2, for example, the control device 90B controls the height of the water-blocking plate 4 of the inlet wall 111B according to the water level on the inlet side of the filtration cassette 50B, that is, in accordance with the vertical position of the filtration layer 2a, thereby maintaining a state in which the water to be treated is prevented from passing through the non-adjacent area A1.

[0133] During filtration operation by the filtration system 200B, for example, in the inlet wall section 111B, the non-adjacent area A1 that is not adjacent to the filtration layer 2a is blocked by the water-blocking plate 4, while the water-permeable area A2 through which the water to be treated can pass is adjacent to the filtration layer 2a. Therefore, the water to be treated flowing through the filtration cassette 50B flows into the housing 1 from the water-permeable area A2, is filtered through the filtration layer 2a, reaches the outlet wall section 112B, and flows out to the outside of the housing 1 (treated water flow path 130). In this way, short paths of the water to be treated are prevented during filtration operation by the filtration system 200B.

[0134] [Cleaning operation using filtration system 200B] As shown in Figure 7, during aeration cleaning of the filtration operation of the filtration system 200B according to Embodiment 2, the control device 90B lowers, for example, the water-blocking plate 6, allowing the water to be treated to pass through part or all of the inlet wall 111B, thereby discharging the cleaning wastewater from inside the housing 1 of the filtration cassette 50B into the treated water flow path 130. In Figure 7, as an example, the height of the water-blocking plate 6 is adjusted so that the water to be treated can pass through the entire inlet wall 111B, that is, so that the entire inlet wall 111B becomes a water-passable area A2. By allowing the water to be treated to pass through the entire inlet wall 111B, the water flow resistance of the filtration cassette 50B is reduced, making it possible to smoothly discharge the cleaning wastewater generated inside the housing 1.

[0135] [Effects and Effects of Embodiment 2] As described above, in the filtration cassette 50B according to Embodiment 2, the side wall 11 of the housing 1 includes an inlet wall portion 111B into which the water to be treated flows, and an outlet wall portion 112B located on the opposite side of the inlet wall portion 111B, with the filtration layer 2a in between, through which the water to be treated flows out. The inlet wall portion 111B (wall where the prevention portion is installed) is provided with a water-pass prevention plate 4 that prevents the water to be treated and the filter material 2 from passing through. The water-pass prevention plate 4 is installed in the inlet wall portion 111B in such a way that it prevents the water to be treated and the filter material 2 from passing through in the area from the position of the bottom wall 12 in the vertical direction to at least the position of the lower end portion 21 of the filtration layer 2a.

[0136] With the filtration cassette 50B configured as described above, the same effects as the filtration cassette 50A according to Embodiment 1 described above can be obtained. Specifically, in the filtration cassette 50B, the inlet and outlet for circulating the water to be treated are provided on the side of the housing 1, so that the inlet and outlet (inlet wall portion 111B and outlet wall portion 112B) can be cleaned during filtration operation. This makes it possible to perform continuous filtration operation for a long period of time. As a result, it becomes possible to perform the filtration operation of the sedimentation tank 100 more efficiently.

[0137] Furthermore, according to the filtration cassette 50B of Embodiment 2, by preventing the passage of water to be treated in the non-adjacent region A1 of the inlet wall 111B that is not adjacent to the filtration layer 2a, short-circuiting of the water to be treated is prevented, and the water to be treated can be filtered effectively. As a result, the filtration operation can be performed more efficiently.

[0138] Furthermore, the filtration system 200B according to Embodiment 2 includes a control device 90B that controls the height of the water flow prevention plate 4 in accordance with the vertical position of the filtration layer 2a. This prevents short-circuiting of the water to be treated even if the vertical position of the filtration layer 2a changes during filtration operation.

[0139] Furthermore, the filtration system 200B according to Embodiment 2 further includes a water level gauge S1 for measuring the water level on the inlet side of the filtration cassette 50B, and the control device 90B controls the height of the water-blocking plate 4 according to the water level on the inlet side. This makes it possible to adjust the height of the water-blocking plate 6 to follow the change in the vertical position of the filtration layer 2a in response to the change in the water level on the inlet side.

[0140] Furthermore, the control device 90B according to Embodiment 2 controls the height of the water-blocking plate 4 in accordance with the vertical position of the filtration layer 2a during filtration operation, and controls the height of the water-blocking plate 4 during washing operation so that the water to be treated can pass through an area of ​​the inlet wall 111B that is wider than or equal to a threshold. This prevents short-circuiting of the water to be treated during filtration operation, while also allowing for the smooth discharge of washing wastewater generated inside the housing 1 during washing operation.

[0141] The water-blocking plate 4 may, for example, have a fixed height. In that case, the height of the water-blocking plate 4 may be set to be greater than or equal to the maximum value of the distance a1 between the bottom wall 12 of the housing 1 and the lower end 21 of the filtration layer 2a.

[0142] [Embodiment 3] Next, the configuration of the filtration system 200 equipped with the filtration cassette 50 according to Embodiment 3 will be described. Hereinafter, the filtration cassette 50 according to Embodiment 3 will also be referred to as the filtration cassette 50C, the control device 90 according to Embodiment 3 will also be referred to as the control device 90C, and the filtration system 200 according to Embodiment 3 will also be referred to as the filtration system 200C. In the following description of Embodiment 3, the differences from Embodiment 1 will be the main focus, and components similar to those in Embodiment 1 will be denoted by the same reference numerals, thus omitting detailed explanations. Figures 8 and 9 are schematic diagrams showing the filtration system 200C according to Embodiment 3. More specifically, Figure 8 is a longitudinal cross-sectional view showing the filtration system 200C according to Embodiment 3 during filtration operation (for example, the later stages of filtration operation), and Figure 9 is a longitudinal cross-sectional view showing the filtration system 200C according to Embodiment 3 during aeration washing during washing operation. Note that in Figures 8 and 9, for convenience, the treated water withdrawal valve 70 and the outlet 150 are shown, and the return mechanism 80 is not shown.

[0143] [Filtration Cassette 50C] As shown in Figure 8, the filtration cassette 50C according to Embodiment 3 differs from Embodiment 1 in that, for example, a water flow prevention plate (prevention part) is installed on both the inlet wall and the outlet wall.

[0144] Specifically, the side wall 11 of the housing 1 in Embodiment 3 includes an inlet wall portion 111B and an outlet wall portion 112A. The inlet wall portion 111B has a water-conducting plate 3 and a water-conducting prevention plate 4, and the outlet wall portion 112A has a water-conducting plate 5 and a water-conducting prevention plate 6. The configuration of the inlet wall portion 111B is the same as that described in Embodiment 2, and the configuration of the outlet wall portion 112A is the same as that described in Embodiment 1, so a detailed explanation is omitted. In Embodiment 3, the inlet wall portion 111B and the outlet wall portion 112A correspond to the "prevention unit installation wall" according to this disclosure.

[0145] [Control device 90C] The control device 90C according to Embodiment 3 controls the height of the water-blocking plate 6 of the outlet wall 112A, similar to Embodiment 1, and controls the height of the water-blocking plate 4 of the inlet wall 111B, similar to Embodiment 2. Specifically, during filtration operation, the control device 90C according to Embodiment 3 controls the height of the water-blocking plate 4 of the inlet wall 111B and the water-blocking plate 6 of the outlet wall 112A, for example, by following the vertical position of the filtration layer 2a, thereby preventing the passage of treated water in at least the non-adjacent region A1 of the inlet wall 111B and the non-adjacent region A3 of the outlet wall 112A.

[0146] For example, the control device 90C controls the height of the water-blocking plate 4 and the water-blocking plate 6 according to the water level on the inlet side of the filtration cassette 50C obtained from the water level gauge S1. For example, the control device 90C controls the height of the water-blocking plate 4 and the water-blocking plate 6 so that they are equal to or greater than the distance a1 between the bottom wall 12 and the filtration layer 2a. As a result, even if the vertical position of the filtration layer 2a changes according to the water level on the inlet side of the filtration cassette 50C, the state in which the passage of water to be treated is prevented is maintained at least in the non-adjacent area A1 of the inlet wall 111B and the non-adjacent area A3 of the outlet wall 112A.

[0147] [Filtration operation using Filtration System 200C] As shown in Figure 8, during filtration operation with the filtration system 200C according to Embodiment 3, the control device 90C controls the height of the water-blocking plate 4 and the water-blocking plate 6 in accordance with the water level on the inlet side of the filtration cassette 50C, that is, in accordance with the vertical position of the filtration layer 2a, thereby maintaining a state in which the water to be treated is prevented from passing through the non-adjacent area A1 of the inlet wall 111B and the non-adjacent area A3 of the outlet wall 112A.

[0148] During filtration operation by the filtration system 200C, the water to be treated flowing through the filtration cassette 50C enters the housing 1 from the permeable area A2 of the inlet wall 111B, is filtered through the filtration layer 2a, and flows out to the outside of the housing 1 (treated water flow path 130) from the permeable area A4 of the outlet wall 112A. Here, since the permeable areas A2 and A4 are adjacent to the filtration layer 2a, the water to be treated passes through the filtration layer 2a at least when it enters the inside of the housing 1 and when it enters the outside of the housing 1. Therefore, short paths are more reliably prevented.

[0149] [Cleaning operation using filtration system 200C] As shown in Figure 9, during aeration cleaning of the filtration operation of the filtration system 200C according to Embodiment 3, the control device 90C lowers, for example, the water flow prevention plate 4 and the water flow prevention plate 6, allowing the water to be treated to pass through part or all of the inlet wall 111B and the outlet wall 112A, thereby discharging the cleaning wastewater from inside the housing 1 of the filtration cassette 50C into the treated water flow path 130. In Figure 9, as an example, the heights of the water flow prevention plate 4 and the water flow prevention plate 6 are adjusted so that the water to be treated can pass through the entire inlet wall 111B and the outlet wall 112A. By allowing the water to be treated to pass through the entire inlet wall 111B and the outlet wall 112A, the water flow resistance of the filtration cassette 50C is reduced, and the cleaning wastewater generated inside the housing 1 can be smoothly discharged.

[0150] Furthermore, at the start of aeration cleaning, the control device 90C may temporarily block more than half of the area of ​​the inlet wall 111B and more than half of the area of ​​the outlet wall 112A by, for example, adjusting the height of the water flow prevention plate 4 and the water flow prevention plate 6. In particular, if more than half of the area of ​​the outlet wall 112A is temporarily blocked, complete mixing of the filter material 2 by swirling flow is promoted at the start of aeration cleaning, and sludge adhering to the filter material 2 becomes easier to remove.

[0151] [Effects and Effects of Embodiment 3] As described above, in the filtration cassette 50C according to Embodiment 3, the side wall 11 of the housing 1 includes an inlet wall portion 111B and an outlet wall portion 112A, the inlet wall portion 111B is provided with a water flow prevention plate 4, and the outlet wall portion 112A is provided with a water flow prevention plate 6.

[0152] With the filtration cassette 50C configured as described above, similar to the filtration cassette 50A according to Embodiment 1 and the filtration cassette 50B according to Embodiment 2, the inlet and outlet for circulating the water to be treated are provided on the side of the housing 1, so that the inlet and outlet (inlet wall portion 111B and outlet wall portion 112A) can be cleaned during filtration operation. This enables continuous filtration operation for a long period of time. As a result, the filtration operation of the sedimentation tank 100 can be performed more efficiently.

[0153] Furthermore, according to the filtration cassette 50C of Embodiment 3, by preventing the passage of water to be treated through the non-adjacent region A1 of the inlet wall 111B that is not adjacent to the filtration layer 2a and the non-adjacent region A3 of the outlet wall 112A that is not adjacent to the filtration layer 2a, short paths of water to be treated can be prevented more effectively. As a result, filtration operation can be performed more efficiently.

[0154] The various embodiments and variations described above may be combined as appropriate.

[0155] (Note) This disclosure includes the following aspects: [Aspect 1] A filtration cassette installed in a treatment tank, through which water to be treated is passed and filtered, A housing having side walls and a bottom wall, The enclosure comprises a filter material housed within the enclosure and forming a filter layer, The side wall includes an inlet wall portion into which the water to be treated flows, and an outlet wall portion located on the opposite side of the inlet wall portion, with the filtration layer in between, through which the water to be treated flows out. The wall on which the prevention part is installed, which is at least one of the inlet wall and the outlet wall, is provided with a water passage prevention part that prevents the water to be treated and the filter material from passing through. The water-pass prevention section is installed in a region of the wall where the prevention section is installed, from the position of the bottom wall in the vertical direction to at least the position of the lower end of the filtration layer, so as to prevent the passage of the water to be treated and the filter material. Filtration cassette. [Aspect 2] A filtration cassette as described in Embodiment 1, The system includes a control device that controls the height of the water-blocking section in accordance with the vertical position of the filtration layer. Filtration system. [Aspect 3] The filter cassette is further equipped with a measuring device for measuring the water level on the inlet side, The control device controls the height of the water flow prevention section according to the water level on the inlet side. The filtration system described in Embodiment 1. [Aspect 4] The control device controls the height of the water-blocking section in accordance with the vertical position of the filter layer during filtration operation in which the water to be treated is filtered by the filter cassette, and controls the height of the water-blocking section in accordance with the vertical position of the filter layer during cleaning operation in which air is blown onto the filter material inside the housing to clean the filter material, so that the water to be treated can pass through an area of ​​the wall on which the blocking section is installed that is wider than or equal to a threshold. The filtration system according to embodiment 2 or 3. [Explanation of Symbols]

[0156] 1: Cabinet 11: Side wall 111: Inflow wall 112: Outflow wall section 12: Bottom wall 14: Opening 2: Filter material 2a: filtration layer 3: Water passage board 4: Water flow prevention plate (an example of a water flow prevention part) 5: Water passage board 6: Water-blocking plate (an example of a water-blocking section) 10: Sedimentation tank (an example of a treatment tank) 50: Filtration cassette 100: Sedimentation tank (an example of a filtration system) 200: Filtration System

Claims

1. A filtration cassette installed in a treatment tank, through which water to be treated is passed and filtered, A housing having side walls and a bottom wall, The enclosure comprises a filter material housed within the enclosure and forming a filter layer, The side wall includes an inlet wall portion into which the water to be treated flows, and an outlet wall portion located on the opposite side of the inlet wall portion, with the filtration layer in between, through which the water to be treated flows out. The wall on which the prevention part is installed, which is at least one of the inlet wall and the outlet wall, is provided with a water passage prevention part that prevents the water to be treated and the filter material from passing through. The water-pass prevention section is installed in such a manner that it prevents the passage of the water to be treated and the filter material in a region of the wall on which the prevention section is installed, from the position of the bottom wall in the vertical direction to at least the position of the lower end of the filter layer. Filtration cassette.

2. A filtration cassette according to claim 1, The system includes a control device that controls the height of the water-blocking section in accordance with the vertical position of the filtration layer. Filtration system.

3. The filter cassette is further equipped with a measuring device for measuring the water level on the inlet side, The control device controls the height of the water flow prevention section according to the water level on the inlet side. The filtration system according to claim 2.

4. The control device controls the height of the water-blocking section in accordance with the vertical position of the filter layer during filtration operation in which the water to be treated is filtered by the filter cassette, and controls the height of the water-blocking section in accordance with the vertical position of the filter layer during cleaning operation in which air is blown onto the filter material inside the housing to clean the filter material, so that the water to be treated can pass through an area of ​​the wall on which the blocking section is installed that is wider than or equal to a threshold. The filtration system according to claim 2.

Images